This article is an attempt to add to our understanding of the map of common law obligations. That there is such a thing is an article of faith among those who believe that the common law is based on reason. Any map does three things: it represents a certain area; it enables us to locate any point on that area by providing us with axes of reference (for example, longitude and latitude) and it identifies certain points on that area as significant. The map of common law obligations covers the set of all possible duties. A duty is located in that set by reference to its pattern (its content) together with its origin (the set offacts sufficient to give rise to that duty). The map of common law obligations identifies all the duties which the common law may give effect to by compelling those who are subject to those duties to comply with them.